The inventive concept relates to semiconductor memories and user devices including such memories. More particularly, the inventive concept relates to fast nonvolatile memories and data management methods suitable for use as a main memory in certain user devices.
In their operative nature, semiconductor memories are volatile or nonvolatile. Volatile semiconductor memories are able to perform read/write operations at relatively high speed, but stored data is lost in the absence of applied power. In contrast, nonvolatile semiconductor memories retain stored data even in the absence of applied power.
Consumer electronics, computers and similar user devices generally include a number of different memory components (or “memories”) that may be respectively or interchangeably used for different purposes. These such memories include a “main memory” that may be used as a primary working space during data transfer, computation and similar user devices functions. Main memories are generally required to be over-writeable and provide fast data access. As a result, Dynamic Random Access Memories (DRAMs) have been conventionally used to implement many main memories. However, DRAM-based main memories consume high levels of power and are volatile in nature.
In recent years, research has been directed to the development of nonvolatile memories capable of providing high data density and large data storage capacity. Flash memory has been widely used in many commercial applications, and primarily in handheld electronic devices to meet these demands. However, research into nonvolatile memory alternatives that may effectively be used as main memory components continues. That is, alternative are being sought that provide a large, nonvolatile, fast access main memory capable of being directly overwritten. For example, ferroelectric RAM (FRAM) that use a ferroelectric capacitor, magnetic RAM (MRAM) that use a tunneling magneto-resistive (TMR) film, phase change RAM that use chalcogenide alloys, and resistive RAM (RRAM) that use one or more variable resistance material(s) as a data storage medium have been specifically considered.
Nonetheless, research and development continues into the development of low power, over-writable, nonvolatile, randomly-accessible memory. More particularly, research continues into certain nonvolatile RAM that may be used in conjunction with a variety of legacy computer system interfaces.
The use of a nonvolatile RAM, however physically implemented, as a working memory is not without significant problems. For example, the retention of stored data by a nonvolatile RAM following power interruption may actually cause operating or re-boot coherency problems in systems using certain interfaces. That is, during a reset or reboot operation caused by a data error, the source data containing the error will be retained in the nonvolatile RAM. Such as occurrence may then result in continuing (or infinite) re-boot failures.